Jig saw



Dec. 2, 1 B. w. HULFISH JIG SAW 6 Sheets-Sheet 1 Filed March 21, 1947 Dec. 2, 1952 B. W. HULFISH J IG SAW 6 Sheets-Sheet 55 Filed March 21, 1947 I; V. W A

Dec- 2, 1952 E. w. HULFISH JIG SAW 6 Sheets-Sheet 4 Filed March 21, 1947 1 wm 9 0/4/4/ v 1952 E. w. HULFISH JIG SAW 6 Sheets-Sheet 6 Filed March 21, 1947 Patented Dec. 2, 1952 JIG SAW Buford W. Hulfish, Chicago, 111., assignor to Birtman Electric Company, a corporation of Illinois Application March 21, 1947, Serial N 0. 736 382 6 Claims.

This invention relates to a jig saw or scroll saw, and particularly to a means for providing a blast of air to keepsawdustaway from the kerf.

A blast of air has been provided in many previous jig saws, or the like, but this air blast has ordinarily been intermittent in operation and only occurs when thesaw blade is moving in one direction. With this apparatus of the present invention, a substantially continuous blast of air is'provided-so that the kerf is kept free of sawdust at all times. With the improved construction, the air blast is set up by the operation of the blade and thus any time the blade is being moved, the air blast is operating. The structure for accomplishing this is simple in construction and trouble-free in operation.

The invention will be described as related to the embodiment shown in the accompanying drawings. Of the drawings, Fig. l is a side elevation of a jig saw embodying the invention with portions broken away for clarity of illustration; Fig. 2 is a top plan view of the saw of Fig. 1; Fig. 3 is a horizontal section taken along line 3-4 of Fig. 1; Fig. 4 is a vertical section taken along line 4-4 of Fig. 3; Fig. 5 is a vertical section taken along line'5--5 of Fig. 4; Fig. 6 is a section taken along line 6-6 of Fig. 4; Fig. 7 is a. section taken along line 'l-'| of Fig. 4; Fig. 8 is-a section taken along line 8-8 of Fig. 4; Fig. 9 is a section taken along line 9-9 of Fig. 4; Fig. 10 is a sectiontaken along line llllil of Fig. 7; Fig. 11 is a section taken along line I l---! l ofFig. l0; 12 is a vertical section takensubstantially through the center of the structure to which the upper end of the saw blade is attached; Fig. 13 is a section taken along line l3|3 of Fig. 12; and Fig. 14.- is a section taken along line l4l4 of Figrlz.

The jig saw shown in the accompanying drawings comprises a base 2Badapted to rest on a table or other. support 2!, a base housing 22 supported on the base 29, a lower arm 23 extending from the base housing in an upwardly inclined direction, an upper arm 24 arranged substantially horizontal and. attached to the extended end of the lower arm 23 by a vertical portion 25, a work support table 26 mounted above the base housing 22 and adapted to support a board 21 or the like .for beingisawed, and a saw blade 28 arranged substantially vertically and extending through a hole 29 provided in the work support table 26.

In Figs. 1 and 12, the saw blade 28 is shown in'its uppermost raised position. In Figs. 4. and 5; the blade is'shown in its loweredposition.

The work support table 26'through which the saw blade 28 extends is provided with two downwardly extending spaced :apart arcuate meme bersfiflon its lower surface with these two members being arranged substantially parallel to. each other and bolted to the bottom of the table. Each of the arcuate members 30 has an inwardly extending arcuate raised portion 30a on its inner surface. The top surface of the base housing 22 is provided with upwardly extending members ill arranged substantially parallel to each other.

and having inwardly sloping sides 32. Each upwardly extending member 3! .is arranged adjacent an arcuate member 30 and is provided with an arcuate groove am which holds a raised portion 30a. Each arcuate member 30 is provided with an arcuate slot 33 and a bolt 34 is provided in each groove with each bolthaving a head 34a and a threaded end 3412 engaging similarly shaped threads in the upwardly extending meme.

her 3 i. With this construction, the table 26 may be turned either backward orfor-ward to any angle desired and held in position by tighten.- ing the bolts 34.

The hole 29 provided in the work support table 25 and through which the saw blade 28 extends is provided with a top countersunk portion 29a extending below the top surface of the table.

The bottom end of the saw blade 28 is removably attached by meansof a small screw 35 to a bolt 36 having an enlarged head portion 36a which holds the screw 35 and a threaded shank portion 361). This shankportion 36b engages similarly shaped threads on the top inner surr face of a hollow stem. The shank portion 36b is provided with a lock nut 360 to lock it against the hollow stem 31. The stem 31 is slidably held in an annularly shaped extended guide member 38 extending down from the inner surface of the top portion 22a of the base housing 22.

In order to reciprocate the stem 31 and thus the saw blade 28,the bottomof the stem is-attached to a transverse hollow portion 39 having a circular cross section-and arranged substantially at right angles tothe stem .31. The

preventing any turning of the stem 31 about its longitudinal axis. The heavy gear wheel 4| is mounted for rotation on an axle 42 extending from a transverse wall 43 within the housing 22. The gear wheel 4| is arranged substantially parallel to the stem 3'! and the guide member 38 and is made heavy or weighted so that it serves as a fly wheel and a counterbalance. Located within the hollow portion 39 is a slidable member 44 which is connected to the gear wheel 4| by a stud 45 having a circular cross section and held in a similarly shaped pocket 46 in the gear wheel. The stud 45 has a portion 45a also of circular cross section, but of larger diameter than the remainder of the stud, engaging a hole in the slidable member 44. The stud 45 is free to rotate in the slidable member 44 and does not rotate in the pocket 46.

On the other side of the transverse wall 43 there is located a motor 41 having a shaft 48 extending through the wall 43 and provided. with a pinion gear 49 engaging the gear teeth of the gear wheel 4|. The shaft has packing material 50 arranged around it. The transverse wall 43 is one wall of the inner housing surrounding the stem 31, guide member 38, hollow portion 39, gear wheel 4|, and pinion gear 49. This inner housing may be kept partly filled with oil so as to provide lubrication to the moving parts of the reciprocating mechanism by means of the gear wheel 4|, the lower portion of which extends below the oil level.

When the motor 41 is operated, it turns the gear wheel 4| and this serves to slide the slidable member 44 back and forth in the transverse hollow portion 39, and at the same time prevents any turning of the stem 3'! about its longitudinal axis. This movement causes reciprocation of the stem 31 and thus of the blade 28. The elongated opening 40 is slightly longer than the diameter of the circle described by the stud 45 during its movement. When the stud 45. the axle 42, and the stem 31 are in a single plane, the stud 45 will be located at substantially the center of the elongated opening 40.

The motor 4'! is provided with four extending equally spaced ears 52, all having base portions lying in substantially a single plane, and the motor is fastened to the transverse wall 43 by bolts 53 extending through the ears 52.

The top end of the saw blade 28 is held in the hollow interior of a collar 54 by means of a screw 55. The collar 54 is attached to the bottom of a hollow stem 56 of non-circular cross section. As shown, the stem 56 is square. The top end of the stem extends up inside a substantially cylindrical housing 51 that is mounted in a hole 58 at the end of the upper arm 24. The top end of the stem 56 is attached to a member 59 extending across the inside of the housing 5! and movable therein. The member 59 is constructed of a packing material 69 held between two parallel plates 6|. The packing material 69 serves to form a seal with the inner surface of the housing 51 and the member 59, therefore, acts as piston. The hollow interior of the stem 56 communicates with the portion of the housing 5'! above the piston through a, hollow threaded plug 62 extending through the piston member 59. The upper end of the housing 5'! is provided with a cap 63 having an opening 93a therein for the entrance of air. Immediately below the opening 63a there is located a flutter valve 64 with the valve being arranged to open as the piston member 59 moves down and close as the piston member 59 moves up.

The stem 56 extends through a guide member 65 extending across the bottom of the housing 51. The portion 65a of the guide member 65 which engages the stem 56 is an oilite bearing or other self-lubricating material and is provided with a square hole through which the stem extends. is provided with three equally spaced arcuate shaped openings 66 communicating with the interior of the housing beneath the piston member 59. These openings need not be equally spaced. Extending between the top of the guide member 65 and the bottom of the piston member 59 there is located a compression Spring 67 with this spring being arranged around the stem 56. The compression spring serves to urge the piston member 59 upwardly.

The housing 51 extends through the hole 59 in the upper arm 24 and also through a hole 66 in a cap member 69 mounted on top of the outer end of the upper arm 24. This cap member is held in place by means of bolts '29 extending through the outer end portion 24b of the'upper arm 24. One of these bolts (not shown) engages a block 1| which is a part of the cap member 69. This block 1| rests against a machined surface on the top of the arm 24 and has an arouate outer surface 12 against which the housing 5! is held. The housing is held in place by means of a strap 73 passing around the housing 51, block TI, and a movable nut 14. The nut 14 and strap 13 are held in place by means of a bolt 15 having a threaded end engaging similarly shaped threads in the nut ?4. This bolt extends through one wall of the cap member 69. By turning the bolt 75, the nut 14 is moved towards this wall to pull the strap toward the wall and hold the housing 51 tightly against the arcuate surface 12. With this construction, the housing 5! may be arranged in any desired position relative to the cap 69 and the upper arm 24 and the housing becomes free by turning the bolt 15 to move the nut 14 away'from this wall. The forward end of the cap 69 extends beyond the end of the upper arm 24 to provide space for an electric light bulb 16. The bottom of the cap 69 below the light bulb 76 is open so the light may shine down on the work.

During the operation of the jig saw, a blast of air is substantially continuously applied to the region adjacent the saw blade 28 to maintain the kerf free of saw dust. When the piston member 59 is moving downwardly, the air is forced out the spaced holes 69 that are located in the guide member 65. During this downward movement, the valve 64 opens to permit air to enter through the hole 63a into the space above the piston member 59. When the piston member 59 moves upwardly, the valve 64 closes and the entrapped air is forced down the hollow stem 56 through the collar 54 and around the top end of the saw blade v29. This air stream is most effective as now the blade is moving upward and drawing saw dust up from the kerf.

In order to hold the saw blade 28 against the Work 21 and also to hold the work against the table 26, there is located adjacent the rear of the saw blade a bar TI arranged parallel to the saw blade and extending through the outer end of the upper arm 24 and the cap member'69.

This bar is held in place by means of a lock bolt 18 extending through the side of the block 1|. If desired the lock bolt 18 can extend through a hole in the upper arm 24 and carry a knob on its outer end so that the bolt can be The remainder of the guide member 65 easilyrloosenedand-tightened; Onithe-bottom' of r thexbar there-:is located a member IQ-extending downwardly and toward I the' saw blade: 23: Mounted anthe -end of thiskmemberthere is located aerotatable wheel" 80 adapted to bear 5 againstthe back of the'sawblade; The mem ber- 19 -isheld'in-place-by ar'bclt 8! extending throughaaslot Haatthewbottom of the bar 11. TheTIJOSitlOIlDf the membervwmaythus be regulated to various distancesrabove the table 25. 10

Mounted on :thetrear surface voflthe member 19 there-is located a downwardly'extending foot 82-=having-'a bifurcatedlower end adapted to straddle the saw blade .28 i and" bear against the workll;

The apparatus forlcontrolling the speed of the motor'zscomprises 2,".131'85136 83 mounted ontherear end ofthe extended motor shaft B8 just behind r the commutatorM; and adapted to berotated by theeplate, azsecondplate 85 mounted on the 20 first-plate 83-in1spaced relationship/thereto by means of spacer and mounting membersdij with saidplate beingdivided into two parts and having outwardly extending portions 8 5a forming an annulus and'witheach plate having two upstanding ears 851), a pair of centrifugally responsive arms 81 mounted-r between ther.plates-s83 rand 85 with- -eachearm rotatable: about a fulcrumi 88 so that: centrifugahforcatends :to force the armsoutwardly and bells cranks 89 alsor-mountedbetweenthe-plates t3 aIId-"SEW-ith eachfibell crank beingrotatablywmounted about-'awfulcrum Eachsbelle crank- 85 r is arranged substantially be tween therplates and has 'one leg: terrain. contact with: an arm- 8 -'t and their otherleg 8 9b lying prim 5 cipaliy-ibetween the plates. As the armdi is forced outwardly @by centrifuaali force, it hears it against-.legaiiiia and forces :it outwardlyalso. The? bellicrank 89 turns around Athe fulcrumm Bit sothat the-other leg-189b is :forcedrinwardly'. Mount-t 40 ed :between z'e'achipair of adjacentears-iitb; there islocated'arsecondibelli crank d i rotatablymounh ed on ia-pin-fl2w extending between the ears." These'bell cranks 9 I are mounted-rat substantially; right angles stoethe plate 83 rand areso arranged. that: ?the free rleg 58% it of-1a bell crank: 89 'ibeai'sw against the outer surface of a leg tla oft-alibell 1'; crank: 9 I The legs 9 I a extend towards the wplate 83; Themtherwiegg I b r of the "bell-a crank 1 ex 4 tendsr towardathe shaft 158 With this :construcetion, the :legs '9 lb of the bell crank t aremoved toward: the outerr'rearend ofthe shaftcdtswhen' the aarms s81; move outwardly under wcentriiugal' force's. Thezlegsji sibib'ear against :a capzmernber 93:slidablysheld:onarthe *rearend of ther'shaft (it-i 5 andlfirotatable:rwith'l'thexshafh. Thesicapumember ber serving to separate ..the arms "when the speed 70 reachesra' predetermined maximums This :masie; mum isx-dependent: upon the :positiorrrof: the co tact arms relative to the adjacent endof theshaft 1 48. a This rentire.zconstructionzis .s. shown randjzd scribedinsgreaterzdetail irrthe Charleen-1:1 Starkw tending {between :the "base :of the :bifurcated pore tiontof.theayokezwith; this pin being held between? spaced apartearstaSQ mounted :on the inner surfacel'ofutheimotor housing: A'lavon ieither::side of. the slot 4117a Bo-thzthc innergcontacti arm 96 and; thenuterxcontact Earm "91 are Frotatably mounted: on the pin 98 with the innertrarm'flfiextendin'g between the :bifurcated portion "Ofliihel outer con tact farm; 91: Bothfcontact'arms 96 and 91 extendaacross -the motor "housing 476: opposite the end'of the cap1'memben93. Onrthe freeend'of the router contact armfil; there. is located an'inwardly extending 1' flange 91b upon which is mountedan outwardly-extending :contact point I00. A 'similar contactpointlfll is mounted on the freeiendrof theinner contactarm 96 with thetwocontact" points being adapted to bear against each rother to close'the electrical 'circuit' to the -motor. The outer contact arm" 91 is provided with a pair of outwardly extending'side portions 197a "extending toward the rear "end of the motor-housing 47a; These'side portions are connected by. a'barSld extending between them; A compression spring 102 'is arranged between the bar "91d and the "central portion 9600f the inner contact arm' 96 opposite the free end of the cap member '93; This central portion 961; is

provided: with: arbuttoni l 03 adapted to be contacted b'y'theizfree end of thecap member-93."

With this construction thecontact arms 96 and 9? may be rotated by means o'fth'e end'portion illd of the outer contact arm 91 about the pin 98. This positions the contact arms relative'to the outer end of 'the shaft 48. As the 'speed'of rotation of the motorincreases, the cap-mem ber-93 bears against the button lil3and forces the inner contact arm 96 outwardly against the This causes separation" compression spring 102. of the contact pointslilfl and [DI and breaks the electrical circuit to the motor;

relative position of the contact arms and 91;"

The end. portions fi'ia'oftheouter contact arm Slismoved by means of a-bar member lMhaving one end rotatably engaging the endportion Ma and the other end extending through the front 221) of thebasehousinglZ: This end of the bar member 64 extends through athickened portion 220 of the front of the base housing and is slidably held therein. Mounted on a pin I05 extending through thisthickened portion 220 is a control button I063. The control button is held on the outer end of the pin by means of a set screw m. The inner end of the pin E05 is provided with a collar I98 that is held on the pin by a key 109. the inner surface of the thickened portion 220 and a compression spring I I!) is arranged between:

the collar I08 and the inner surface of thethick-n ened portion 220. This spring serves tohold the control buttoneltfitagainst the outer surface or thetfront portionfZZb oftheb'ase housing 22. Thee As the speed i of the motondecreasesythe compression'spring H32 forces the contact points back together so that the electrical circuit is again closed; Ascan be seen, the speed of rotation depends upon the I This collar m3 is spaced from inner surface of the control button I06 is provided with a substantially circular cam surface ill against which the outer end of the bar I04 bears. As the button 106 is turned, the cam surface IH causes the bar I04 to be moved longitudinally. This movement of the bar turns the contact arms 96 and 91 around the fulcrum pin 98 and positions the arms relative to the rear end of the motor shaft 48. With the parts at the positions shown in Figs. 4 and 10, the motor will operate at its slowest speed'as the inner contact arm 96 is at its nearest distance to the end of the shaft 48. The bar I04 can move the outer contact arm 9'! even closer to the end of the shaft 48 thereby compressing the spring I02 and separating the contacts H30 and IM. This creates an ofi position.

One of the important features of this invention is the mounting of the motor on the inner housing 51 which serves as the oil casing and connecting the motor directly through gearing to the means for reciprocating the blade. This reduces vibration to a minimum so that the jig saw runs quietly and smoothly. In most prior jig saws vibration and noise were problems primarily due to the inefficient means employed in translating rotary motion to reciprocating motion. Thus prior jig saws were often jerky, erratio, and noisy. In the present jig saw the weighted over-size gear wheel i! that serves as a fly wheel also aids in cutting down vibration and noise. The gear wheel 4| is provided with a cut out section Ma on its front face so located that the pin 45 is between this cut out section and the shaft 42. This serves to at least partially compensate for the reciprocating weight of the reciprocating mechanism and reduces the magnitude of vibration. If desired a similar cut out section could be provided on the opposite face of the gear, or on both faces.

The above features also permit the employment of a speed control for the motor as the motor runs smoothly and quietly at all speeds without slipping between the motor and the saw blade. In many prior jig saws, the motor could not be operated at low speeds even if it were so desired because the means for translating the motion were subject to slipping.

Other features of the invention are claimed in my copending applications Serial No. 736,4:62, filed March 22, 1947, and Serial No. 741,973, filed April 17, 19 .7, and in the Charles H. Sparklin application Serial No. 736,491, filed March 22, 1947. 7

Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description unless otherwise specified but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. In a jig saw including a support table, a saw blade extending therethrough and means for reciprocating the blade, support means comprising a hollow housing above the blade, a member extending in sealing relationship across the inside of the housing and movable therein, a hollow shaft of non-circular cross-section attached to the movable member, means on the end of the shaft for holding the corresponding end of the blade, said hollow shaft communieating with the space above the movable memberand with the area, adjacent the correspond ing end of the blade to provide an air passage,

guide means at the end of the housing adjacent the blade provided with a hole through which the shaft extends and also provided with a perforation adjacent the shaft, a cap across the end of the housing that is opposite the blade and having an opening therein, and a valve in said opening with the valve being arranged to open when the movable member moves away from said cap and to close when said member moves toward said cap.

2. In a jig saw including a table, a saw blade extending therethrough and an arm above said table having its free end located above said blade, 9, cap member removably held on top of said free end, said cap member having an opening therein aligned with but spaced from a similar opening provided in said free end, a block attached to said cap member and located between the cap member and said free end, said block having one end adjacent said openings, a hollow housing extending through said openings and contacting said one end of the block, means within said housing for supporting the upper end of said saw blade, and means engaging said block and said housing for holding the housing in pcsition against said block.

3. The jig saw of claim 2 wherein said cap member is hollow with the block being located within the cap member and bearing against the top of said free end of the arm.

4. In a jig saw including a table, a saw blade extending therethrough and an arm above said table having its free end located above said blade, a cap member removably held on top of said free end, said cap member having an opening therein aligned with but spaced from a similar opening provided in said free end, a block attached to said cap member and located between the cap member and said free end, said block having one end adjacent said openings, a hollow housing extending through said openings and contacting said one end of the block, means within said housing for supporting the upper end of said saw blade, and a strap member extending around said block and said housing for releasably holding the housing in position against the block.

5. In a jig saw including a table, a saw blade extending therethrough andan arm above said table having its free end located above said blade, a hollow cap member removably held on top of said free end, said cap member having an opening therein aligned with a similar opening provided in said free end, a block located within and attached to said cap member and having the lateral sides spaced from the corresponding sides of the cap member, said block having one end adjacent and between said openings and having its bottom surface on the top surface of said free end, a hollow housing extending through said openings and contacting said one end'of the block, means within said housing for supporting the upper end of said saw blade, a strap member extending around said block and said housing for releasably holding the housing in position against the block, and means extending through a Wall of said cap member and engaging the strap member for adjusting the tenin for admission of air under reduced pressure when the piston is moved away from said closure, the opening in said hollow shaft extending through said piston, a guide closure at the saw end of the cylinder having an air blast opening directed toward the saw blade, and an air orifice in the hollow shaft adjacent the blade, movement of the piston toward said cap causing a blast of air to be directed through said hollow shaft and shaft air orifice and movement 10 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,036,810 Dufault Aug. 27, 1912 2,033,846 Mitchell Mar. 10, 1936 2,073,430 Tautz Mar 9, 1937 2,116,123 Ocenasek May 3, 1938 2,165,002 Ocenasek July 4, 1939 

